1. Field of the Invention
The present invention relates generally to power distribution equipment and, more particularly, to circuit interrupters with fuse protection.
2. Description of the Related Art
Two primary objectives of the electric utility industry in the delivery of electrical power are safety and reliability. Since the late 1920s, AC secondary network systems have been used in certain locations such as downtown business districts and commercial areas in order to provide a high degree of service continuity. In such an AC secondary network system, a plurality of secondary mains surround the area being served, such as a city block, and are connected with one another to form a secondary network grid at low voltage to which the customer loads are connected.
Electrical power is supplied to the secondary network by a plurality of high voltage transmission lines. Each high voltage transmission line delivers power to the network through network transformers. The transformers reduce the high voltage from the transmission lines to a lower voltage suitable for distribution to the customers.
In such secondary network systems, a failure of any one transmission line will not result in an interruption of service to the customers since electrical power will be supplied to the customers over the remaining transmission lines. When a failure or fault occurs in a high voltage transmission line or in one of its associated network transformers, the station end of the transmission line, that is, the end of the transmission line closest to the generating station, is disconnected from the system by opening a feeder circuit breaker. In addition, it is necessary that all of the network transformers on the failed transmission line be disconnected from the secondary network by some type of protective device to prevent power from the secondary network from being fed back through the network transformers to the fault. The protective device used for such purpose is the network protector.
The network protector consists of a specially designed circuit breaker with a closing and opening mechanism that is controlled by a relay. When the network protector is closed, the relay operates to trip the network protector upon a reversal of power flow. The relay acts to close the network protector when, and only when, the proper voltage conditions exist across the network protector.
Network protectors typically have been located outdoors either above ground or below ground and thus have been protected by a sealed enclosure. When a network protector is approached for maintenance, testing, or repair, the network protector must be electrically and physically disconnected from the power distribution equipment on both the network transformer side and the secondary network side. Historically, this consideration dictated the use of a rollout-type or draw-out-type circuit breaker which could be disconnected and rolled out of its enclosure for maintenance, testing, and repair.
Network protectors typically have additionally included fuses on each phase between the circuit breaker and the network transformer or between the circuit breaker and the network. Such fuses have been provided as a backup current interruption device that operates in the event of a failure of the circuit breaker. The fuses extending between the circuit breaker and the secondary network typically have either each been disposed in separate fuse housings that are disposed at the exterior of the sealed enclosure or been disposed internally within the sealed enclosure within which the circuit breaker is disposed. Such fuse housings typically have been molded out of an insulative material such as epoxy and include a cover which, when in place, seals the fuse within the fuse housing. While such fuse housings have been generally effective for their intended purposes, such fuse housings have not, however, been without limitations.
It is known that fuses generate heat during operation, and such heat must be dissipated through the fuse housing to the surrounding atmosphere. It is known that the heat generated by a fuse increases quadratically with the current passing through the fuse. As such, the heat dissipation characteristics of the fuse housings have limited the current-carrying capability of the fuses disposed within the housings. It is thus desired to provide an improved fuse housing having improved heat dissipation characteristics which permits a fuse disposed within the improved fuse housing to be employed in relatively higher current carrying applications than was previously possible.
Previously known fuse housings have included a pair of conductors extending from the interior of the fuse housing to the exterior thereof to permit the fuse to be connected between the circuit breaker and the network. At elevated current levels, particularly at fault current levels, the magnetic fields generated around such conductors can result in significant forces being applied to the conductors when the conductors of different phases are disposed closely adjacent one another. Such forces on the conductors have been known to fracture the fuse housings. It is thus desired to provide an improved fuse housing that is resistant to such fracturing due to forces from the conductors.
Accordingly, an improved fuse housing includes a main body and a cover and is configured to receive a fuse therein. The main body includes a plurality of fins that are configured to increase the surface area of the fuse housing in order to enhance the heat dissipative characteristics of the fuse housing. The main body is formed with a cavity within which the fuse can be disposed, and further includes a pair of conductors extending between the interior of the fuse housing and the exterior thereof that are connectable with the fuse. The cavity is configured to minimize the quantity of insulative air between the fuse and the fuse housing, which facilitates the transfer of heat from the fuse to the fuse housing and thus to the atmosphere. Each of the conductors includes an excess quantity of studs for connection with the fuse in order to enhance the conduction of heat away from the fuse. The cover is fastened to the main body with a sufficient number of fasteners to permit the cover to be a stressed member and to help resist fracturing of the fuse housing due to magnetic and other forces applied by the conductors.
As such, an aspect of the present invention is to provide an improved fuse housing that can be employed in conjunction with a network protector or other electrical device.
Another aspect of the present invention is to provide an improved fuse housing having enhanced heat dissipation characteristics.
Another aspect of the present invention is to provide an improved fuse housing having a plurality of fins formed thereon.
Another aspect of the present invention is to provide an improved fuse housing having a main body that is formed to include a cavity that is configured to receive a fuse therein, with the cavity being configured to minimize the quantity of insulative air between the fuse and the main body.
Another aspect of the present invention is to provide an improved fuse housing having a pair of conductors, wherein the conductors each include an excess number of fasteners for connection with a fuse to enhance the conduction of heat from the fuse to the conductors.
Another aspect of the present invention is to provide an improved fuse housing having a main body and a cover, in which the cover is securely fastened to the main body with a sufficient number of fasteners that the cover can become a stressed member and resist the fuse housing from fracture upon the application of forces thereto.
Accordingly, an aspect of the present invention is to provide a fuse housing that is structured to receive a fuse, in which the general nature of the fuse housing can be stated as including a main body, the main body including at least a first fin, the at least first fin being structured to dissipate heat from the fuse housing to the atmosphere, the main body being formed with a cavity, a first conductor, a second conductor, a cover, the cover being disposed over the cavity, and the cavity being structured to receive therein the fuse in electrically conductive engagement with the first and second conductors.
Another aspect of the present invention is to provide a current interrupter, the general nature of which can be stated as including a fuse housing, the fuse housing including a main body, the main body including at least a first fin, the at least first fin being structured to dissipate heat from the fuse housing to the atmosphere, the main body being formed with a cavity, a first conductor, a second conductor, a fuse, the fuse being disposed in the cavity, the fuse being electrically conductively engaged with the first conductor, the fuse being electrically conductively engaged with the second conductor, a cover, and the cover being disposed over the cavity.
Another aspect of the present invention is to provide a network protector, the general nature of which can be stated as including an enclosure, first current interruption means disposed internally within the enclosure, second current interruption means disposed externally to the enclosure, the second current interruption means including a fuse, the second current interruption means including a fuse housing, the fuse housing including a main body, the main body including at least a first fin, the at least first fin being structured to dissipate heat from the fuse housing to the atmosphere, the fuse housing including a first conductor, the fuse housing including a second conductor, the fuse being electrically conductively engaged with the first conductor, the fuse being electrically conductively engaged with the second conductor, the main body being formed with a cavity, the fuse being disposed in the cavity, the fuse housing including a cover, and the cover being disposed over the cavity.